Electrochemical cells comprise a cathode, an anode and an electrolyte interposed therebetween. The electrochemical cells are often defined as liquid or solid cells and this refers merely to whether the electrolyte interposed between the anode and the cathode is a liquid or a solid. Solid electrochemical cells are well known in the art and present many advantages over conventional liquid batteries such as improved safety features, lighter weight, etc. Non-aqueous lithium electrochemical cells are discussed in U.S. Pat. Nos. 4,472,487, 4,668,595, 5,028,500, 5,441,830, 5,460,904, and 5,540,741.
The anode comprises a compatible anodic material which is any material which functions as an anode in an electrochemical cell. Such compatible anodic materials are well known in the art and include, by way of example, lithium, lithium alloys, such as alloys of lithium with aluminum, mercury, nickel, zinc, and the like, and intercalation based anodes such as carbon, WO.sub.3, and the like. The cathode comprises a compatible cathodic material which refers to any material which functions as a positive pole (cathode) in an electrochemical cell. Such compatible cathodic materials are well known in the art and include, by way of example, manganese dioxide, molybdenum trioxide, sulfides of titanium and niobium, chromium oxide, copper oxide, vanadium oxides such as V.sub.2 O.sub.5, V.sub.6 O.sub.13, LiV.sub.3 O.sub.8 and the like. The particular compatible cathodic material employed is not critical. When the electrochemical cell is a secondary cell, then the compatible cathodic material employed is one which is capable of being recharged (e.g., LiV.sub.3 O.sub.8, V.sub.6 O.sub.13, MoO.sub.3, and the like).
Composite electrode refers to cathodes and anodes wherein the cathode includes materials in addition to compatible cathodic materials and the anode includes materials in addition to compatible anodic materials. Typically, the composite electrode contains a polymer which acts to bind the composite materials together and an electrolytic solvent. Composite electrodes are well known in the art. For example, a composite cathode can comprise a compatible cathodic material, a conductive material, an electrolytic solvent, an alkali salt, and a solid matrix forming polymer. Similarly, for example, a composite anode can comprise a compatible intercalation anodic material, an electrolyte solvent and a solid matrix forming polymer.
Secondary lithium ion cells and batteries employing composite electrodes are typically fabricated in the discharged state which means that the anode comprises intercalation carbon materials and the cathode comprises a suitable lithiated cathodic material, e.g., lithiated manganese oxide. Prior to use, the cell must be charged with external energy so that lithium ions from the cathodic material are intercalated into the carbon material of the anode. It has been found that during the initial charge/discharge cycles the cell generates a considerable amount of gases. These gases would be entrapped in the cell unless they are removed by a conditioning process prior to sealing the package encasing the cell.